How to install text color of an QLabel?

[tumanovalex]

On the standard form there is an QLabel with the text, would like to make at form loading text color of an the QLabel red, and after a file choice - green. Has tried:

QPalette t_palette = ui->lbFileName->palette();
t_palette.setColor(QPalette::Text, Qt::gray);
ui->lbFileName->setPalette(t_palette);

QPalette t_palette = ui->lbFileName->palette();
t_palette.setColor(QPalette::Text, Qt::gray);
ui->lbFileName->setPalette(t_palette);

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Color doesn't change. Prompt, please, as it to make.